There's been some grumbling in the past about the unreliability of really ludicrously long URLs sent to the API.

We've always considered this suboptimal, but the underlying technical constraints (http.sys + IIS + .NET 3.5) made fixing this a very arduous endeavor.

Well, ardor has been endured and the API should accept any reasonable construction now.

Be aware that once you go past 100 ids all bets are off as something will kill such requests. If its not the API itself, you'll probably get something unexpected back.

Also be aware that standard HTTP timeouts and the like apply, so really massive requests on expensive routes run the risk of Gateway Timeouts (not to mention whatever client side timeouts you may be imposing or have imposed upon you).